The problem with value based arguments is it’s not absolute, it depends on the person making the purchase and their financial position, and how much they value those differences.
Every difference in this hobby is overstated, it’s the nature of wasting time on forums over analyzing it.
DAC’s in particular are difficult to distinguish between in fast A/B switching tests, I’d argue that’s not really all that interesting, I’ve had multiple higher end DAC’s here at that same time with the ability to keep any or all of them, and with extended listening I have always had clear preferences, for one or another.
Part of the issue I think people who focus on measurements have with subjective assessments, is the language used doesn’t map to measurements. You’ll see midcentic, on something that measures with a flat FR, or terms like faster where there isn’t a measurable difference in slew rate. It’s just difficult to map the language to metrics, that doesn’t discount the perception, it just implies the language is imprecise.
I’m a bit flumoxed that anyone would think all amps sound the same, I’d personally have a hard time telling a difference between the low Sinad, high feedback designs, but outside of that there are very obvious differences to me.
I’ve been designing and building amps for myself for a while now, I do measure everything I can, but short of knowing what bad looks like I’m not sure I could point to the measurements I take and say that’s why it exhibits good bass grip or air or whatever. My current best indicators for a “good sounding” amp are the shape of the harmonic distortion, and how that changes with input level, and the phase response. But I exclusively use low feedback designs with only local feedback (if any) and as a result I’m usually only aiming for 2nd Harmonic distortion in the -70dB range at listening levels.
I often a prototype on strip board with whatever resistor and capacitors I have in my parts bins to validate before ordering PCB’s and higher quality parts, and even with identical circuits and very close measurements, the final designs often sound somewhat different to the prototypes.
But one of the biggest surprises to me was around the impact of physical packaging and internal layout.